U.S. patent application number 17/058635 was filed with the patent office on 2021-07-08 for screw closure with controlled seal.
The applicant listed for this patent is Bericap GmbH & Co. KG. Invention is credited to Gunter Krautkramer.
Application Number | 20210206545 17/058635 |
Document ID | / |
Family ID | 1000005521267 |
Filed Date | 2021-07-08 |
United States Patent
Application |
20210206545 |
Kind Code |
A1 |
Krautkramer; Gunter |
July 8, 2021 |
SCREW CLOSURE WITH CONTROLLED SEAL
Abstract
The invention concerns a plastic closure for fitting on to the
neck of a liquid container in positively locking and sealed
relationship comprising a head plate (1) provided for covering a
container opening and an outer seal (7) which is circumferential
along the edge of the head plate (1) and is provided for engagement
with the outside of a container neck (20) defining the container
opening, and an inner seal (5) which is circumferential within the
outer seal (7) and parallel thereto and which is provided for
engagement with the inside of the container neck, wherein the outer
and the inner seals (7, 5) respectively extend approximately
perpendicularly or slightly inclined from an inside (11) of the
head plate (1). To provide a closure and also a container having a
closure which generally prevent the closure being blown off under a
high positive pressure it is proposed according to the invention
that the outer seal (7) has a weakened region (6, 6', 6'') in at
least one circumferential portion so that the outer seal (7)
becomes unsealed at a lower internal positive pressure than when
the outer seal is of a configuration without the weakened
region.
Inventors: |
Krautkramer; Gunter;
(Budenheim, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bericap GmbH & Co. KG |
Budenheim |
|
DE |
|
|
Family ID: |
1000005521267 |
Appl. No.: |
17/058635 |
Filed: |
July 2, 2019 |
PCT Filed: |
July 2, 2019 |
PCT NO: |
PCT/EP2019/067690 |
371 Date: |
November 24, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B65D 2251/20 20130101;
B65D 39/08 20130101; B65D 51/1661 20130101 |
International
Class: |
B65D 51/16 20060101
B65D051/16; B65D 39/08 20060101 B65D039/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 5, 2018 |
DE |
10 2018 116 295.2 |
Claims
1. A plastic closure for fitting on to the neck of a liquid
container in positively locking and sealed relationship comprising
a head plate (1) provided for covering a container opening and an
outer seal (7) which is circumferential approximately parallel to
the edge of the head plate (1) and is provided for engagement with
the outside of a container neck (20) defining the container
opening, and an inner seal (5) which is circumferential within the
outer seal (7) and parallel thereto and which is provided for
engagement with the inside of the container neck, wherein the outer
and the inner seals (7, 5) respectively project from an inside (11)
of the head plate (1) in the direction of the container neck to be
covered by the head plate, characterised in that the outer seal (7)
has a weakened region (6, 6', 6'', 16) in at least one
circumferential portion, wherein the configuration of the closure
is such that the outer seal yields in the weakened region (6, 6',
6'', 16) at a lower internal positive pressure than without the
weakened region, in particular yields at a lower internal positive
pressure than in the remaining regions of the outer seal.
2. A plastic closure according to claim 1 characterised in that it
is in the form of a screw closure, wherein the screw closure (100)
has a head plate (1) and a cylindrical cap skirt (2) with a female
thread (3) which define an axis (50) of the closure, wherein the
outer and inner seals are in the form of webs which extend
circumferentially in an annular configuration at a spacing relative
to the cap skirt and parallel thereto and the weakened portion is
preferably restricted to an angle sector (a) measured with respect
to the axis.
3. A screw closure according to claim 1 characterised in that it
has a sealing region which is an axial region of the outer seal of
constant inside diameter, which at least partially includes the
central third of the axial length of the outer seal and corresponds
at maximum to the axial length of the outer seal.
4. A screw closure according to claim 1 characterised in that the
weakened region (6, 6', 6'', 16) is formed by a groove (6') or rib
(6'') which extends on the inside surface of the outer seal and
which extends on the inside of the outer seal over the axial extent
of the sealing region of the outer seal.
5. A screw closure according to claim 2 characterised in that the
groove (6') or the rib (6'') extends substantially axially and is
of a cross-section of less than 0.05 mm.sup.2, in particular less
than 0.02 mm.sup.2 and for example is of a width and a depth of 0.1
mm each.
6. A screw closure according to claim 1 characterised in that the
weakened region (6, 6', 6'', 16) comprises a circumferential
portion of the outer seal, that is axially shortened in the angle
sector (a).
7. A screw closure according to claim 4 characterised in that the
axial length of the shortened circumferential portion is less than
2/3 of the axial length of the outer seal outside the weakened
region (6, 6', 6'', 16).
8. A screw closure according to claim 1 characterised in that the
weakened region (6) comprises a circumferential portion of the
outer seal (7) with a wall thickness which is reduced in relation
to the rest of the outer seal (7), wherein the outer seal (7) in
the weakened region (6) thereof is of the same internal radius as
the outer seal (7) elsewhere but is of a smaller external
radius.
9. A screw closure according to claim 5 characterised in that the
reduced wall thickness of the outer seal in the weakened region (6)
extends axially over at least a part of the central axial third of
the length of the outer seal and is less than half of the wall
thickness outside the weakened region, wherein the extent of the
weakened region (6) in the circumferential direction is preferably
restricted to preferably a circumferential angle of between
20.degree. and 90.degree..
10. A screw closure according to claim 8 characterised in that the
weakened region of reduced wall thickness extends axially from a
free axial end at least into the upper axial third, with respect to
the axial extent of the outer seal outside the weakened region.
11. A screw closure according to claim 1 characterised in that a
portion (14) in the form of an annular disk of the head plate (1)
between the outer and inner seals defines an axial abutment surface
(4) for the end face (24) of a container mouth opening and the
maximum outside diameter of the inner seal (5) is provided at an
axial spacing of between 0.4 and 1.0 mm from the abutment
surface.
12. A screw closure according to claim 1 characterised in that a
circumferential groove is provided in the internal surface (11) of
the head plate at the transition from the portion (4) of the head
plate (1), that is in the form of an annular disk, to the inner
seal (5).
13. A screw closure according to claim 1 characterised in that the
inner seal (5) is of an axial length of at least 2 mm with an end
portion which conically tapers from its maximum diameter towards
its axially free end.
14. A screw closure according to claim 1 characterised in that the
maximum outside diameter of the inner seal is greater by at least
1.5 mm than its maximum inside diameter.
15. A screw closure according to claim 1 characterised in that the
screw closure comprises polyethylene and the wall thickness of the
head plate within the region embraced by the outer seal is at a
maximum 1.2 mm.
16. A container for liquids having a container neck on which a
plastic closure is fixedly and sealingly fitted, characterised in
that it has a plastic closure according to claim 1.
17. A container according to claim 16 characterised in that the
container neck has a male thread and the plastic closure is a screw
closure.
18. A container according to claim 16 or claim 17 characterised in
that the maximum external radius of the inner seal is greater by
0.3 to 0.7 mm than the nominal internal radius of the container
neck at the respective position.
19. A container having a screw closure according to claim 1
characterised in that a constant internal radius of the outer seal,
insofar as same comes into sealing contact with the outside (22) of
the container neck (20), is 0.3 to 0.7 mm smaller than the nominal
constant external radius of the container neck (20) in the region
of the sealing contact with the outer seal.
Description
[0001] The present invention concerns a plastic closure for fitting
on to the neck of a liquid container in positively locking and
sealed relationship comprising a head plate provided for covering a
container opening and an outer seal which is circumferential
approximately parallel to the edge of the head plate and is
provided for engagement with the outside of a container neck
defining the container opening, and an inner seal which is
circumferential within the outer seal and parallel thereto and
which is provided for engagement with the inside of the container
neck, wherein the outer and the inner seals respectively project
from an inside of the head plate in the direction of the container
neck.
[0002] Substantially the circumferential seals extend parallel to
each other and approximately perpendicularly or slightly inclined
relative to a plane defined by the head plate.
[0003] In particular the invention concerns a screw closure of
plastic for liquid containers, wherein the screw closure has a head
plate, a cylindrical cap skirt with a female thread, which define
an axis of the closure, and an annular inner seal which after being
fitted on to the container neck is to be brought into engagement
with the cylindrical internal surface of the container neck and an
annular outer seal which is to be brought into engagement with the
cylindrical outside of a container neck, wherein the outer and
inner seals respectively extend in a predominantly axial direction
from the inside of the head plate.
[0004] Such plastic closures are used inter alia for drinks
bottles. In that respect the present invention concerns in
particular closures for such containers in which an uncontrolled
positive pressure can occur. That applies in particular to
containers which are filled with a liquid which in principle is
fermentable and within which accordingly a considerable positive
pressure can build up (after contamination with germs).
[0005] When such containers are filled with the products in
question they generally do not have a high internal pressure, with
the exception of a slight positive pressure which is deliberately
applied by filling with an inert gas and which substantially serves
to make the bottles which usually comprise thin-walled PET material
overall stable and thus stackable, in which case typically a
plurality of containers are combined together to constitute a pack
and are stacked one upon the other in that form.
[0006] In that respect some segments of the market have
increasingly found there is a wish on the part of consumers to
obtain the container content in a form which is as pure and natural
as possible and not to extend the shelf life of the content in
question like for example fruit juice or smoothies with
preservatives. It will be appreciated that after opening such
drinks have a comparatively short best before date, even if they
are filled under asceptic conditions. It can therefore happen that,
after a consumer has purchased such a container, in particular
after it has been first opened, the consumer leaves it for a
prolonged time and possibly also at an unfavourable (warm)
location, whereby fermentation processes can begin because of an
initially low level of germ contamination in the liquid in the
container. Upon fermentation gases are typically produced and they
in turn increase the pressure in the interior of the container in
an uncontrollable fashion. Even if the containers and the
corresponding closures are designed for a slight positive pressure
(for example 2 bars), in order to make it easier to stack
corresponding packs as mentioned above, a pressure occurring due to
fermentation can be a multiple higher than the pressure required
solely for ensuring stackability, under which the containers were
originally filled with an inert gas.
[0007] As is usual in the state of the art, the closure according
to the invention has two mutually independent seals of which one
comes into sealing contact with the inside and the other with the
outside of a corresponding container neck (deleted text moved to
page 3:).
[0008] As the containers with the exception of the slight positive
pressure already described above for making them stackable are
substantially pressureless the closures used for that purpose are
generally axially relatively short and also have a relatively
steep, usually multi-flight thread, which allows quick opening and
closing of the container, while on the other hand affording the
closure only a comparatively slight holding action and also only
limitedly permitting venting or breathing of the container during
the short opening process.
[0009] The result of this is that, in the attempt to open a
container which is under a relatively high internal pressure, the
closure is already explosively blown off the container neck after
just a short rotary angle and in that case can seriously injure a
user, in particular if delicate body parts like for example an eye
are hit by the closure when it is blown off.
[0010] It will be appreciated that the invention is not restricted
to that specific situation of use but concerns closures for all
containers in which a positive pressure of for example more than 4
bars prevails, in particular if such an increased pressure can
uncontrolledly occur.
[0011] In that respect by virtue of its geometrical arrangement and
configuration the inner seal only withstands a limited positive
pressure. To limit the internal pressure by the inner seal
therefore either no or only slight additional measures are
therefore required, as is explained hereinafter. In the known
closures however the outer seal can withstand a very considerable
positive pressure.
[0012] With that background in mind the object of the present
invention is to provide a closure and also a container having a
closure, which generally prevent the closure being blown off under
a high positive pressure.
[0013] That object is attained in that the outer seal has a
weakened region in at least one circumferential portion, wherein
the closure is of such a configuration that the outer seal in the
weakened region yields at a lower internal pressure than without
the weakened region, in particular yields in the weakened region
earlier than in the other regions.
[0014] In a screw closure the weakened region preferably extends
over an angle sector which is measured with respect to the axis and
which depending on the respective nature of the weakened can be
limited to less than 1.degree. circumferential angle, but in other
embodiments can also be limited to an angle sector of 20 to
90.degree..
[0015] Under some circumstances the weakened region could also
extend over the entire circumference, for example in the form of a
groove extending in a spiral configuration.
[0016] In general terms therefore the object is attained in that
the closure from the outset does not allow a correspondingly high
positive pressure, that is to say becomes lacking in sealing
integrity and allows gas to escape when the pressure in the
interior of the container exceeds a given predeterminable amount,
more specifically without a pressure relief valve which is to be
additionally fitted.
[0017] The lower portion (facing away from the head plate) of the
inner seal is typically bevelled radially inwardly and is curved
inwardly at the end in order to ensure when the closure is being
fitted on to the container neck that the inner seal slides into the
opening of the container neck. Therefore, the lower end of the
inner seal, when the outwardly disposed bead bears against the
inside of the container neck, is at a marked internal spacing
relative to that inside. In addition on its outside the inner seal
has a radially outwardly projecting region or bead which, after
corresponding compression by the container neck, bears sealingly
under an elastic prestressing against the inside of the container
neck.
[0018] A positive pressure which occurs in a container provided
with the closure generally has the result that the head plate of
the closure bulges up. In that case the inner seal is moved a
distance upwardly for free opening of the neck and at the same time
the inner seal tilts radially inwardly and the pressure of the gas
or the liquid which can act from the exterior on the lower portion
of the inner seal additionally contributes to radially inward
pivotal movement of the inner seal so that as from a certain
positive pressure it at least locally lifts away from the inside of
the container neck. The inner seal thus becomes non-sealing.
[0019] The internal pressure then acts on the outer seal. In that
case however the bulging movement of the head plate also causes a
reduction in the diameter of the outer seal at least at its
attachment to the head plate, which leads to the outer seal being
pressed even more firmly against the container neck. Without
measures to reduce the internal pressure the above-mentioned risk
of the closure abruptly blowing off upon opening of the closure
occurs.
[0020] By virtue of the weakened region of the outer seal, which is
deliberately provided according to the invention however the outer
seal also yields at a lower pressure than would be the case if the
outer seal did not have any weakened region. In that way the
otherwise higher internal pressure is reduced and the risk of a
closure being blown off the container neck is completely or at
least substantially eliminated. The weakened region is accordingly
a means for specifically limiting increased pressure.
[0021] By virtue of a suitable geometrical configuration of the
weakened region, which can also be readily determined by
experiment, it is possible to properly adjust the desired increased
pressure value at which the weakened region of the outer seal
yields and allows (partial) escape of the gas under pressure in the
container. In general the weakened pressure will be set such that
the pressure at which the outer seal opens in the weakened region
is somewhat above the pressure at which the container is filled in
any case for stability reasons, that is to say a pressure of
between 1 and 2.5 bars, in which respect precisely observing given
pressure values is not an important consideration so long as only
the opening pressure of the weakened region is markedly below the
values which could cause the closure to be dangerously blown off
the container neck. An appropriate upper limit for the internal
pressure of containers provided for example for non-carbonated
drinks is about 3 to 4 bars for a closure having a two-flight
thread with an approximately 360.degree. contact angle and a
nominal diameter of 38 mm. Such an appropriate upper limit for the
pressure varies with the diameter of the neck and the configuration
of the thread and can tend to be greater in the case of a smaller
diameter and also smaller in the case of a larger diameter.
[0022] The outer seal of the screw closure according to the
invention desirably has a region which is referred to hereinafter
as the sealing region and which is generally viewed as the axial
region which is in sealing contact with a container neck.
Specifically, without reference to a (generally standardised)
container neck, that is a region of then outer seal of constant
inside diameter which at least in part embraces the central third
of the axial length of the outer seal. Because of a rounding at the
outer edge of a container mouth opening, as is provided as standard
in most containers under consideration, in order to ensure that,
when the closure is fitted on to the container neck, the outer seal
slides on to the outside of the container neck, the region of the
outer seal, that is near to the head plate, is not or is scarcely
in contact with the container neck.
[0023] The end, remote from the head plate, of the outer seal which
is generally in the form of a ring or an annular web is generally
slightly radially outwardly curved or bevelled (as viewed in an
axial section), also in order to make it easier when fitting the
closure on to the container neck for it to slide on to the
container neck, in which case the outer seal overall is radially
enlarged and stretched so that it bears under an elastic
prestressing against the container neck and in that way withstands
a relatively high internal pressure. In that respect it is to be
assumed that the sealing region of an outer seal includes at least
a part of the central axial third of the outer seal and the sealing
region can then be suitably defined with reference solely to the
closure.
[0024] Therefore even the radially outwardly curved lower end
portion of the outer seal does not bear against the container neck
and cannot make any noteworthy contribution to the sealing effect.
The actually sealing region of the outer seal is disposed
approximately in the central third with respect to the axial length
of the outer seal. That is the above-defined sealing region which,
in accordance with the present invention, by virtue of specifically
targeted measures, is to be influenced or set to a given opening
pressure.
[0025] In a variant of the invention it is provided that the
weakened region comprises a circumferential portion of the outer
seal, that is of a reduced wall thickness in relation to the rest
of the outer seal, wherein in that weakened region the outer seal
is of the same internal radius as the outer seal elsewhere, but is
of a smaller external radius.
[0026] By virtue of the inside diameter which is constant
throughout such an outer seal bears against the outside surface of
a container neck with the sealing region thereof along its entire
circumference and provides a good sealing action within the
required pressure range for which the container and the closure is
designed under normal conditions. As however the wall thickness in
the weakened region is less than the outer seal in its remaining
region that portion of reduced wall thickness in the event of an
increased pressure in the interior of the container can more easily
stretch and push radially outwardly so that the outer seal lacks a
sealing action in that region when the pressure exceeds a
predetermined limit value.
[0027] Accordingly such a design configuration affords a closure
which provides for a complete seal under normal circumstances and
which is completely sealed off by an inner seal and also by an
outer seal, wherein it is only in the case of a greater internal
pressure (for example >4 bars) that the head plate bulges
greatly upwardly whereby the inner seal tilts radially inwardly and
lifts axially and/or radially off the internal surface of the
container neck, whereupon the higher pressure which acts on the
outer seal is then released by way of the respective weakened
region.
[0028] In an embodiment of the invention the reduced wall thickness
extends in the axial direction from a free axial (lower) end into
the upper third of the outer seal, with respect to the axial length
of the outer seal outside the weakened region.
[0029] For the lifting-off movement of the inner seal inter alia
the maximum outside diameter of the inner seal, that is to say the
so-called "bead" of the outer seal, is provided at an axial spacing
of between only 0.4 and 1.2 mm, preferably less than 1 mm, from the
abutment surface, so that that region is very greatly influenced by
any movements of the head plate, in particular a bulging movement
thereof, and thus at least after a certain increased pressure is
reached, and at least at places lifts off the inside surface of the
container neck. Gas (or also liquid) which is under an increased
pressure can then escape into the region in front of the outer
seal, wherein the weakened region of the outer seal limits the
pressure which occurs, insofar as, when a limit pressure is
exceeded, it allows the pressurised gas to pass. In the event of a
sufficient bulge movement of the head plate the sealing bead of the
inner seal which defines the maximum diameter thereof can be lifted
into the region of the rounded configuration of the inner edge of
the bottle neck or beyond so that at any event the inner seal
allows gas to pass towards the outer seal or into the region
between the outer and inner seals.
[0030] Another embodiment provides that the weakened region
comprises a circumferential portion of the outer seal, that is
axially shortened in the angle sector a. By virtue of the fact that
the outer seal is shortened in a circumferential portion and the
shortening also includes the sealing region an only still axially
very short portion of the sealing region bears against the outside
of the container neck in the angle sector, and the result of that
is that the outer seal in that region which is weakened in that
way, solely by virtue of the fact that it is also lifted a distance
axially by the bulging head plate, yields at a relatively low
increased pressure in the container interior and locally lifts off
the container neck so that any increased pressure is relieved in
that way. At the same time such an axially shortened sealing region
is always still sufficient to ensure sealing of the screw closure
in the pressureless state, that is to say when the pressure on both
sides of the outer seal is approximately equal or is limited to the
regular positive pressure (<2 bars) of the container. In
particular an embodiment provides that the axial length of the
outer seal in the weakened region is less than two thirds of the
axial length of the outer seal outside the weakened region.
[0031] That measure also provides that the outer seal and therewith
the closure generally becomes non-sealing at a markedly lower
internal pressure or reduces an increased internal pressure at an
earlier time than a closure having an outer seal without the
weakened region. Without a weakening as is provided according to
the present invention the outer seal remains sealed until a PET
bottle bursts.
[0032] The two above-mentioned embodiments can also be readily
combined together as shown in the embodiment of FIG. 1. With a
combination of a weakened portion of reduced wall thickness and
axial shortening of the outer seal in the same circumferential
sector or portion the axial shortening can be about a third in
relation to the outer seal in the remaining region and the wall
thickness should be less than half the wall thickness of the outer
seal outside the weakened region, in which case the reduced wall
thickness extends axially into the upper third of the outer seal,
with respect to the axial length thereof outside the weakened
region.
[0033] In a further variant it is provided that extending on the
internal surface of the outer seal is a groove or a rib which at
any event extends over the axial width of the sealing region of the
outer seal. A corresponding groove would provide a small passage
which bridges over the sealing region and by way of which gas under
pressure in the interior of the container, which has possibly
already passed the inner seal, can be discharged outwardly without
the pressure in the interior of the container being further
increased.
[0034] A web or a rib which extends radially inwardly on the
surface of the outer seal and which otherwise also extends over the
axial width of the sealing region acts in a similar fashion as on
both sides of such a rib the sealing surface of the outer seal is
lifted off the bottle neck and in that way also forms a passage for
a gas under pressure.
[0035] These embodiments accordingly have an outer seal which
permanently has a deliberately set slight leakage. By virtue of a
capillary-like passage of for example 0.03 mm.sup.2 cross-section
that leakage can already sufficiently allow gas to pass, as is
liberated for example in a fermentation process. In regard to the
dimension of the cross-section of a specifically provided
capillary-like passage it is also possible to take account of the
fact that, in relation to a closure which is acted upon with liquid
from the interior (for example a bottle which is tipped over or is
upside down), that passage under some circumstances also has to
allow liquid to pass through. Such a capillary opening on the other
hand does not represent any problem under normal sales and storage
conditions because under such conditions the inner seal still
effectively seals off the container interior in relation to the
surroundings.
[0036] It will be noted that if possible it should also be
prevented that impurities and in particular fermentation-causing
germs can pass through the outer seal to the mouth of the container
neck and possibly into the container neck, by virtue of such a
groove or by a projecting region of a sealing surface, as are
implemented by a rib. For that reason a corresponding groove and
similarly also a corresponding rib should be of a cross-section
which is as small as possible and which fulfils the foregoing
conditions and which for example is less than 0.05 mm.sup.2, in
particular less than 0.02 mm.sup.2, wherein a corresponding groove
and similarly a corresponding rib for example could of a width and
also a depth of 0.1 mm each so that the overall cross-section does
not exceed 0.01 mm.sup.2. The passage cross-section at least for
gas can also be markedly less than the above-mentioned values and
for example can be only 0.0001 mm.sup.2 which is sufficient to
reduce a gas pressure which builds up slowly, but which on the
other hand opposes a great resistance to the entry of contamination
and germs, as long as a reversed pressure difference does not
occur.
[0037] Therefore such a small passage provides that a pressure
prevailing in the interior of the container, which also lifts the
inner seal off its engagement with the internal surface of the
container neck, is only very slowly and substantially continuously
relieved.
[0038] Insofar as no positive pressure or no increased pressure
occurs in the interior of the container at any event the inner seal
prevents the ingress of germs and the like into the container and
the risk that possibly solely the container neck mouth becomes
contaminated is very slight in the above-described embodiments
having a groove or a rib at the internal surface of the outer seal,
in consideration of the small cross-section of the groove or
rib.
[0039] The fact that the inner seal is of an axial length of at
least 2 mm with an end portion which conically tapers from its
maximum diameter to its axially free end also contributes to the
inner seal more easily lifting off the internal surface of the
container neck. The pressurised gas in a container does not have
any axial counterpart in the conical region outside the internal
cross-section of the inner seal and can thus contribute to the
inner seal being pressed radially inwardly and thereby losing
sealing integrity.
[0040] Overall for yielding of the inner seal in the event of an
excessively high internal pressure it has also proven to be
desirable if the maximum outside diameter of the inner seal is
greater by at least 1.5 mm than its maximum inside diameter.
[0041] In general the maximum outside diameter of the inner seal is
also smaller than the minimum inside diameter of the outer seal
because a container mouth opening still has to be accommodated
between them, in which case the corresponding inclined run-on
surfaces and rounded configurations at the seals and/or at the
container neck mouth make it possible for the maximum outside
diameter of the inner seal and the minimum diameter of the outer
seal to differ only slightly and in particular by markedly less
than corresponds to the wall thickness of the container neck.
[0042] Between the outer and inner seals the head plate has an
annular portion defining an axial abutment surface for the end face
of a container neck mouth. The wall thickness in the region of that
annular abutment surface can be the same as in the central region
of the head plate, but it can in particular also be larger or
smaller, in which respect the latter is preferred to make the head
plate more easily moveable so that it bulges more in the event of
an increased pressure in the interior of the container.
[0043] The invention in that respect also concerns a container
having a plastic closure, wherein the container has a container
neck designed for positively locking and sealing engagement with a
plastic closure according to one of claims 1 to 14. In particular
the invention also concerns a container having a container neck
with a male thread and a screw closure, wherein the maximum outside
radius of the inner seal is greater by 0.2 to 0.4 mm than the
nominal inside diameter of the bottle neck. Conversely however the
inside diameter of the outer seal, that is constant in the sealing
region, is smaller by 0.2 to 0.4 mm than the nominal outside
diameter of the container neck. This provides that both seals bear
under a prestressing against the inside and the outside
respectively of the container neck while the end face thereof butts
axially against the annular abutment surface of the head plate,
that is between the outer seal and the inner seal.
[0044] Further advantages, features and possible uses of the
present invention will be apparent from the description hereinafter
of preferred embodiments and the accompanying Figures in which:
[0045] FIG. 1A shows a section containing the axis of a closure
through a screw closure fitted on to a bottle neck in accordance
with a first embodiment of the invention, wherein the view is
limited to the region of the seals and shows a normal portions of
the outer seal,
[0046] FIG. 1B shows a section perpendicular to the axis of the
closure in FIG. 1A corresponding to section line B-B,
[0047] FIG. 2 shows a section corresponding to FIG. 1A of a closure
on a container under an increased pressure,
[0048] FIG. 3A shows a section through the portion diametrally
opposite to the portion shown in FIG. 1A of the same closure as
shown in FIG. 1A with an outer seal weakened in a segment,
[0049] FIG. 3B shows a section along line B3-B3 in FIG. 3A,
[0050] FIG. 4 shows a view corresponding to FIG. 3A with an
additionally illustrated contour of the outer seal outside the
weakened region,
[0051] FIG. 5A shows a plan view of a portion of the internal
surface of an outer seal according to a further embodiment, having
a recess in the sealing region,
[0052] FIG. 5B shows a horizontal section through a closure as
shown in FIG. 5A, the section plane extending through the recess
and the section showing only a portion of the closure on a bottle
neck,
[0053] FIG. 6A shows a plan view of a portion of the internal
surface of an outer seal according to a further embodiment, having
a projection in the sealing region,
[0054] FIG. 6B shows a horizontal section through a closure as
shown in FIG. 6A, the section plane extending through the
projection and the section showing only a portion of the closure on
a bottle neck,
[0055] FIG. 7A shows a section similar to FIG. 1A of a further
embodiment,
[0056] FIG. 7B shows a horizontal section through a closure as
shown in FIG. 6A, the section plane extending through the weakened
region of the outer seal and the section showing only a portion of
the closure on a bottle neck, and
[0057] FIG. 8 for providing a better overview shows a cross-section
through the complete closure as shown in FIGS. 1 and 3.
[0058] FIG. 1 shows an axial section through the edge of a
container neck with a closure 100 fitted thereon. The container
neck is described hereinafter as a bottle neck and shows the
contour of a bottle neck edge of a PET bottle with a 30 or 43 mm
thread.
[0059] The inner seal 5 is shown here overlapping with the internal
surface of the bottle neck 20, which however is only intended to
indicate that the external surface of the inner seal, in particular
the bead 5' provided on the outer surface, bears with elastic
prestressing against the internal surface of the bottle neck 20, as
is also shown in FIG. 2, FIG. 2 additionally showing a head plate 1
which is bulged up by an increased internal pressure. The increased
pressure also provides that the conical outside surface between the
maximum diameter of the bead 5' and the lower free end of the inner
seal 5 is acted upon by the increased internal pressure so that, as
from a certain internal pressure, the inner seal 5 or its outwardly
projecting bead lifts off the internal surface of the bottle neck
20 and thus allows the pressure to escape into the region between
the outer seal 7 and the inner seal 5.
[0060] The state shown in FIG. 2 corresponds to a situation in
which the inner seal 5 is lifted off and tilted to such an extent
that it is lifted off the internal surface 22 of the bottle neck
and is now non-sealing. The rounded configuration provided in
accordance with usual standards at the inner upper edge of the
bottle neck in turn contributes to the inner seal at least locally
losing sealing contact with the bottle neck as from a certain
pressure.
[0061] FIG. 1A shows a part of the closure 100 having a head plate
1, a cap skirt 2 with a screw thread 3 and an inner seal 5 and an
outer seal 7. When the closure 100 is screwed on to a bottle neck
20 the mouth of the bottle neck 20 is moved between the outer seal
7 and the inner seal 5, more specifically generally until the end
face 24 of the bottle neck mouth bears against an abutment surface
4 of the annular portion 14 at the underside of the head plate 1,
that is between the two seals 5 and 7.
[0062] The conically inwardly tapering lower portion of the inner
seal 5 and the lower portion of the outer seal 7, which portion
expands conically or in a rounded configuration, like the rounded
configurations at the upper edge of the bottle neck mouth,
contribute to the bottle neck 20, when the closure 100 is being
fitted in place, being displaced between the inner seal 5 and the
outer seal 7 and not compressing a seal which bears against the end
face 24 of the bottle neck.
[0063] FIG. 2 shows (once again only as a portion) a head plate 1
which is bulged up under an increased internal pressure so that the
internal pressure triggers a lack of sealing integrity of the inner
seal 5, wherein the internal spacing between the bead 5' of the
inner seal 5 and the inside 22 of the bottle neck 20 is shown on a
somewhat exaggerated scale to illustrate the effects which occur.
By virtue of the bulging action in respect of the head plate 1
which is also promoted by a smaller wall thickness d of the head
plate 1 in the region of the annular portion 14 of the head plate 1
(see FIG. 4) the inner seal 5 has a tendency to tip inwardly, as
initially already occurs due to the radially inward displacement of
the bead 5' upon engagement with the inner sealing surface of the
bottle neck 20. In the region radially within the inner seal 5 the
head plate 1 is of a somewhat greater wall thickness D, wherein the
different wall thicknesses d, D are not a necessary feature but can
simplify or promote the desired overpressure limitation in respect
of the closure.
[0064] As an alternative to a reduced wall thickness for the
annular portion 14 or in addition a groove can be provided at the
transition from the abutment surface 4 and the inner seal 5 on the
inside of the head plate 1, which makes the inner part of the head
plate 1 with the inner seal 5 even more moveable with respect to
the radially outer portion 14, and this makes it even easier for
the head plate 1 to assume its bulged configuration and for the
inner seal 5 to tilt and axially lift off until it loses its
sealing integrity. With a sufficiently high internal pressure also
acting on the outside of the inner seal 5, insofar as it does not
have an opposite surface acted upon with pressure in the axial
direction the bead 5' lifts off at least at some locations from the
internal surface 22 of the bottle neck 20 so that the pressure can
escape until the bulge in the head plate 1 has correspondingly
reversed and the elastic return forces of the inner seal move the
bead 5' of the inner seal 5 into sealing engagement with the bottle
neck again.
[0065] FIG. 3A shows the same closure as FIG. 1A with the section
plane however extending through a weakened region 6 of the outer
seal 7.
[0066] In this case the weakened region 6 comprises an optionally
axially shortened portion 6 of the outer seal 7, which portion is
of a reduced wall thickness and which admittedly is of the same
inside diameter as the outer seal 7 in the rest of the region, but
is of a markedly smaller outside diameter. FIG. 3B shows a section
through the line B3-B3 in FIG. 3A. The inner seal 5 bears against
the internal surface 21 of the bottle neck 20 (the overlap of the
inner seal 5 with the bottle neck 20 in FIG. 3A is only intended to
represent the stress-free state before the inner seal 5 or the bead
5' thereof is pressed inwardly by the bottle neck).
[0067] The upper third of the outer seal 7, adjoining the head
plate, is disposed in the region of a radius of curvature at the
upper edge of the neck mouth and thus does not come into contact
with the bottle neck and the lower third is already radially
enlarged in order in that way, when fitting the closure on to a
bottle neck, to make it easier for the mouth of the bottle neck 20
to slide into the intermediate space between the two seals 5 and 7.
If now the seal 7 is shortened over a certain angle sector .alpha.
which for example can be 30.degree. to half or the entire axial
length of the outer seal 7 then in that region there is still only
an axially relative short portion of the outer seal 7 in contact
with the outside 21 of the bottle neck 20, in which case a
relatively slight increased pressure within the outer seal 7 is
sufficient to lift that relatively short portion which is still in
sealing contact off the outside 21 of the bottle neck 20 and thus
cause pressure relief.
[0068] The outer seal 7 of which two end portions are shown in the
angle portion illustrated in FIG. 3B is not only axially shortened
in the weakened segment within the angle sector .alpha. but is also
replaced by a weakened region 6 which is of reduced wall thickness
but which is of the same inside diameter as the inner seal 7
elsewhere. Under normal conditions, that is to say when no or only
a slight increased pressure of for example 2 bars prevails in the
region between the inner seal 5 and the outer seal 7 the weakened
region 6 of the outer seal therefore also bears sealingly against
the outside 22 of the bottle neck 20 and provides protection from
the ingress of germs prior to first being put to use, that is to
say on the way from the filler to the consumer.
[0069] The dimensional relationships between the weakened region 6
of the outer seal 7 are moreover shown once again in FIG. 4 where,
in addition to the weakened region 6 shown in section, the contour
of the outer seal 7 has also been shown again, as is to be found in
the regions of the outer seal 7 outside the weakened region 6. It
can also be seen from FIG. 4 that the wall thickness d of the head
plate in the region between the inner seal 5 and the outer seal 7
is somewhat smaller than the wall thickness D radially within the
inner seal 5.
[0070] FIG. 8 shows the complete closure in the sectional plane in
FIGS. 1A and 3A. In this case FIG. 1A corresponds to the region I
enclosed in the broken line in FIG. 8 and FIG. 3A corresponds to
the region III enclosed in the broken line in FIG. 8.
[0071] In the weakened region 6 on the right-hand side in FIG. 8
the outer seal 7 is axially shortened and reduced in its wall
thickness whereby the outer seal 7 is more easily stretchable in
the weakened region 6 and yields at a lower internal pressure than
would be the case with a uniform configuration of the outer seal 7
with full wall thickness and axial length as in the region I and in
the other region.
[0072] FIG. 5A shows a small portion of the head plate 1 with the
seal 7 extending downwardly from the head plate 1, FIG. 5A being a
plan view on to the internal surface of the outer seal 7, which is
normally in sealing contact with the external surface 22 of the
bottle neck.
[0073] In this case the internal surface of the outer seal has a
small groove-like recess 6' which in the axial direction bridges
over the region in which the seal bears in other respects sealingly
against the outside 22 of the bottle neck 20. This is
diagrammatically shown once again in FIG. 5B in a section passing
through the recess 6'. For practical purposes it is sufficient if
the cross-section of the groove-like recess 6', as can be seen in
FIG. 5B, is less than 0.5 mm.sup.2, in particular less than 0.2
mm.sup.2. The approximately semicircular recess 6' in the section
in FIG. 5B could for example be of a radius of 0.1 to 0.2 mm.
[0074] FIGS. 6A and 6B represent a further embodiment in which,
instead of a recess 6', there is a radially inwardly projecting web
or a rib or a projection 6''. Even if the wall thickness of the
outer seal 7 is constant in the circumferential direction of the
outer seal and on both sides of the projection or the rib 6''
nonetheless short portions of the inner seal 7 on both sides of the
rib 6'' are lifted off the external surface 22 of the bottle neck
20, which effectively means that two small recesses 6' of
wedge-shaped cross-section are in turn formed on both sides of the
rib 6''. Here too the rib 6'' is of such a size that the
cross-section of the recesses 6' formed in that way in total is not
more than 0.5 mm.sup.2, preferably less than 0.2 mm.sup.2. It will
be appreciated that here too the rib 6'' extends in a straight line
or curved in the axial direction over the sealing region of the
outer seal 7 so that the recess 6' makes a connection of the space
between the outer and inner seals with the outside of the bottle
neck 20.
[0075] FIG. 7 finally shows yet a further embodiment in which the
outer seal 7 has been axially shortened in an angle region .alpha.
so that in the angle sector .alpha. of the weakened region 16 there
is only a very small contact axially between the outer seal 7 or
the weakened region 16 and the bottle neck 20 or its external
surface 22. It is of such a dimension that, when the head plate
assumes the bulging configuration, the outer seal in spite of its
proximity to a notional pivot point of the bulged part of the head
plate 1 is still displaced sufficiently axially upwardly to open a
gas passage.
[0076] The invention is based in substance on two effects, namely
on the one hand making use of the upward bulging of the head plate,
that occurs at the internal pressure, in order firstly to open the
inner seal to such an extent that unwantedly high internal pressure
of for example more than 3 bars is passed to the outer seal.
Secondly that outer seal is also weakened in an angle sector in
such a way that, when acted upon with the pressure exceeding for
example 3 bars, it also yields and the pressure can be relieved
from the container by gas discharge.
[0077] Those effects are also achieved inter alia by using the
material polyethylene, in particular HDPE, for the closure, in
conjunction with a wall thickness for the head plate of less than 2
mm, preferably less than 1.0 mm, as well as an inner seal, the bead
of which is relatively close to the head plate and provides a
sealing effect there and thus upon the movement of the region in
question of the head plate at an increased internal pressure is
axially displaced sufficiently far.
[0078] The invention also concerns in particular a combination of a
container neck or a container with a plastic closure, wherein the
maximum outside diameter of the outer seal is between 0.2 and 0.4
mm larger than the corresponding inside diameter of the container
neck opening, while the inside diameter of the outer seal is also
about 0.2 to 0.4 mm smaller than the corresponding outside diameter
of the container neck in the respective angular position. The
closure according to the invention is particularly well suitable
for containers with cylindrical container necks which are of an
inside diameter of 40 or 30 mm but can also be used for smaller
closure diameters of for example 28 mm. The above-described
embodiments are accordingly adapted in respect of their dimensions
to corresponding standardised container necks or bottle necks.
LIST OF REFERENCES
[0079] 1 head plate [0080] 2 cap skirt [0081] 3 screw thread on the
closure [0082] 4 abutment surface (internal surface of the head
plate between the seals 5, 7) [0083] 5 inner seal [0084] 5'
radially projecting region, bead [0085] 6 weakened region [0086] 6'
weakened region [0087] 6'' weakened region [0088] 7 outer seal
[0089] .alpha. angle sector [0090] 11 internal surface of the head
plate [0091] 14 annular portion of the head plate 1 with the
abutment surface 4 [0092] 16 weakened region [0093] 20 bottle neck
[0094] 21 external surface/outside of the bottle neck [0095] 22
internal surface of the bottle neck [0096] 100 closure
* * * * *